Hydraulic metal-tube extrusion presses



April 27, 1965 H. ROBRA 3,180,124

HYDRAULIC METAL-TUBE EXTRUSION PRESSES Filed July 22, 1964.

- INVENTOR. F He/maf Rora United States Patent 3,180,124 HYDRAULIC METAL-TUBE EXTRUSION PRESSES Helmnt Rohra, Walifriedsweg 24, Mulheim (Ruhr), Germany Filed July 22, 1964, Ser. No. 384,476 Claims priority, application Germany, Nov. 16, 1959, Sch 26,999 4 Claims. (Cl. 72-22) This invention relates to metal working and more particularly to an extrusion press and control system, this application being a continuation-in-part of my co-pending application Serial No. 67,230, filed November 4, 1960, and now abandoned.

Hydraulic metal-tube extrusion presses are known, with a container for a billet to be extruded, a die arranged at the end of the container, and a piercing mandrel guided through the press ram.

In a press of this kind it is also known that the mandrel rod bears against an abutment located on a mandrel cross-bar, and is displaceable in the extrusion direction independently of the mandrel cross-bar. This known movement of the mandrel (relative stroke) obviates the risk of a breakage of the front end of the mandrel, which may occur if the extrusion material flowing through the die exerts such a strong frictional pull upon the mandrel that the mandrel, already weakened by the heat, is no longer able to withstand this pull. With the known construction, therefore, the mandrel, carried along by the extrusion material, executes, relatively to the press ram, during the extrusion, a relative stroke, the magnitude of which is dependent upon the material to be extruded, the length of the billet, and the degree of conversion of the material. The degree of conversion is here determined by the ratio of the cross-sectional area of the container bore to the cross-sectional area of the extruded product. The magnitude of the relative stroke is variable over a wide range, and depends, amongst other things, upon the magnitude of a braking action upon the mandrel, provided by a pneumatic pad (or a me chanical spring) interposed between the mandrel rod and its cross-bar.

The provision of the pneumatic pad or of a hydraulic spring involves an additional expenditure on construction parts, and an increase in the length or in the height of the press.

The object of this invention is to obviate more particularly the last-mentioned disadvantage, and it consists in the feature that a controllable throttle, for instance, a controllable pressure-reducing valve, is fitted, as a brake, in the outlet pipe of the mandrel-rod retracting cylinder. If, with such a construction, after the termination of the piercing, and at or after the commencement of the extrusion, the mandrel-rod retracting cylinders maintain communication with the waste-water discharge by way of the throttle or pressure-reducing valve, it is only the adjusting of the throttle or pressure-reducing valve that determines (apart from the unavoidable intrinsic resistance of the piercing appliance) the magnitude of the braking force acting upon the mandrel rod,- so that the relative stroke remains within a tolerable order of magnitude.

The throttle or pressure-reducing valve is preferably adjustable in dependence upon the position of the ram in the container, namely, in such a way that the throttle aperture is opened progressively wider as the ram penetrates further into the container.

During the extrusion the mandrel cylinder is in general connected with the waste-water discharge, so that it does not exert either a forward impulse or a braking influence upon the motion of the mandrel. Now with thin mandrels, however, the pull of the metal issuing Biddjfid Patented Apr. 27, 1965 from the die, even when it is so great that it might break the mandrel, i no longer great enough to overcome the frictional resistance of the piercing appliance. This can be remedied by changing over the mandrel cylinder, after the completion of the piercing travel, to low-pressure water. There can then be exerted upon the piercing piston so much pressure that the intrinsic friction of the piercing appliance is eliminated. The same result is obtained if a tank of low-pressure Water is connected to the piercing cylinder by way of a controllable non-return valve, which allows pressure water to flow out of the piercing cylinder only when it isin a controlled open position, and if there is connected to the low-pressure water tank an excess-pressure relief valve which allows liquid to flow out of the tank to the waste water in the event of over-filling.

The aim of reducing the over-all height or the overall length of the press is further served if the piercing appliance, in a manner known in itself, is arranged in the platen, the travel of the piercing appliance in the press platen being in any case greater, by the relative stroke, than the length of the container plus the necessary piercin g over-travel.

The invention is illustrated by way of example in the accompanying drawing in which the single figure shows a portion of an extrusion press in section and shows diagrammatically the control system for the press.

By 1 is denoted the stationary bolster of a press, which,

accommodates a pressure plate 2, against which bears a die 3. A container 4, displaceable in the direction of extrusion, is pressed, by means, not shown, against the die 3. A press ram 5 is mounted on a press platen 6, which carries at the rear end a press plunger '7, which is slidable in a stationary press cylinder 8. The press cylinder 8 has lateral flanges 9, which are connected with the bolster 1 by tension rods It). The platen 6 may be guided upon a bottom track, not shown, or on the tension rods 19. In the press ram 5 a mandrel 11 is slidable, which is mounted on a mandrel cross-bar 12. The mandrel cross-bar 12 carries two mandrel-retracting cylinders 13, into which mandrel-retracting plungers 14 extend when the mandrel cross-bar 12 moves to the left relative to the platen 6. The plungers 14 are mounted fast on the platen 6. The mandrel cross-bar 12 also carries a rearwardly extending piercing plunger 15, which slides in a piercing cylinder 16, constructed within the press plunger 7.

Low pressure liquid can be admitted to and discharged from the cylinder 8 through a pipe 20. The supply of pressure fluid to the cylinder 8 may be controlled by an inlet valve 58, and the discharge of fluid from the cylinder 8 may be controlled by a discharge valve 59'. The valves 58 and 59 may be electrically controlled. The piercing cylinder 16 is connected, by way of a pipe 21, which penetrates in a fluidtight manner through the wall of the press cylinder 8, with a pressure hose 22, to which is connected a pipe line 23, which in its turn has a connection at 24 to a high-pressure fluid source. In the pipe 23 is arranged an electrically controlled admission valve Stl. The pipe 23 also has a connection, by way of an electrically controlled outlet valve 57 and an electrically controlled valve 51, with a low-pressure water tank 25, which is fed by a pump 26, and is connected to a drain by way of an excess-pressure valve 40. The valve 51 may be controlled to permit water to flow from the low-pressure tank 25 into the cylinder 16,- but not in the opposite direction, or may be controlled to permit flow in both directions. The pressure-liquid source 24 is connected, by way of an electrically controlled admission valve 53, with a pipe 27, to which is connected a pressureliquid hose 28, which has access, through a slot 29 in the platen 6, to one mandrel-retracting cylinder 13, which is die.

' sired manner.

means, the outlet valve 59 is closed and the inlet valve 58 connected by way of a pipe 30 with the other mandrel: retracting cylinder 13. To the pipe 27 is also connected an electrically controlled exhaust valve 54, which communicates by way of a pipe 31 with a suitable drain. Between the pipe 27 and the pressure-liquid source 24 is moreover interposed a non-return valve 52, and to the pipe 27 is furthermore connected another pipe 32, which leads to the drain. In this pipe 32 is interposed an electrically controlled valve 55, which, in the open position, permits flow of fluid from the pipe 27 to the drain pipe 32 by way of an electrically controlled throtle valve 56. The throttle valve 56 may be adjusted by hand, but electrical control is preferable.

In the platen 6 is arranged a switch 35, which is connected by an electrical conductor 36 through a relay 41 with an electrical switch box 37 containing suitable conventional relays. The mandrel cross-bar 12 engages the switch 35 when it has traversed a path in relation to the platen 6, which corresponds to the length of the con tainer 4 plus some further travel of the mandrel into the The switch 35 elfects, by way of the switch box 37, the closing of the outlet valve 54 and of the mandrel admission valve 5%), and at the same time opens the mandrel outlet valves 57 and 51 and the valve 55. Upon the mandrel cross-bar 12 engaging the switch 35, the piercing stroke is completed.

After a definite length of travel of the press ram 5, the platen 6 comes into contact with a switch 33, which acts, through the medium of the relay 42 in the switch box 37, to increase or decrease the action of the throttle 56. i

As shown in the drawing, the press is in inoperative position and in this condition the inlet valve 58 in the fluid pressure supply pipe 26 is closed and the outlet valve 59 is open. Furthermore, valves 50, 53, 55 and the valve 57 disposed in the low pressure water supply pipe 70 to the piercing cylinder 16 are closed and the check valve 53. is in a' condition to permit flow of water from the tank 25 to the piercing cylinder 16 as shown by the arrow 51:: but not in the opposite direction. The drain valve 54 in the pipes 31 is open.

When it is desired to utilize the press for an extrusion operation, a billet, not shown, is positioned between the container 5 and the press ram 5 and supported inany de- By means of suitable electrical control is opened to admit pressure fluid to the ram cylinder 3,

thereby-moving the ram piston '7 forwardly to move the ram 5 into engagement with the billet to press the same into the container 4 and after completion of the insertion of the billet into the container 4, the inlet valve 58 is closed and the outlet valve 59 opened.

In order to start the piercing operation,:the valve 57 is opened which permits low pressure water'to flow from the tank 25 through the check valve 51 and pipe 22 to the piercing cylinder 16 which causes the piercing piston to move forwardly, thereby bringing the piercing mandrel 11 into engagement with the billet disposed in the container 4. Thereafter, the valve 5% is opened which admits high-pressure fluid through the pipe 23 to the piercing cylinder 16 which serves to drive the piercing mandrel 11 through the billet disposed in the container 4 and abutting the die 3. It is to be noted that during this operation Water cannot flow into the low pressure water tank since the check valve 51 prevents flow thereof in this direction. Also, during this operation, the ram plunger 7 moves rearwardly in the cylinder 8, thereby forcing water out of the cylinder 8 through the pipe 2-9 and outlet valve 59. During the piercing operation the retracting cylinders 13 move with respect to the retracting pistons 14 and consequently, water is forced out of the retracting cylinders 13 through the pipe 23 and drain valve 54.

As a safety measure, there is provided a checkvalve 52 connecting the pipe 27 and the high-pressure fluid supoperation.

ply pipe 23 and the check valve 52 permits flow of fluid only from the pipe 27 to the pipe 23 but not in the opposite direction. In the event the drain valve 54 does not function properly or does not openat the proper time, an excess pressure might be developed in the retracting cylinders 13 and in the event such a situation exists, this excess pressure will be discharged through the check valve 52 into the high-pressure pipe 23, thereby precluding damage to the apparatus.

Upon completion of the piercing operation, the mandrel cross-bar 12 engages the switch which through the switch box 37 operates to close the valves and 54, open the valve and at the same time, the check valve 51. is opened to permit flow of fluid in either direction therethrough. The press is now in condition to start the extruding operation and in order to initiate the same, the outlet valve 59 is closed and the inlet valve 53 is opened to introduce pressure fluid into the ram cylinder 8, thereby forcing the ram piston '7 and the ram 5 forwardly to press the billet disposedin the container 4 through the die 3 and since the mandrel 11 has penetrated the billet and remains therein a tube-like member is extruded between the mandrel and the die 3.

During the extruding operation, the mandrel 11 tends to adhere to the material being extruded and in many instances, the force exerted on the mandrel as a result of this adhesion is suflicient'to break the mandrel. This invention serves to prevent breakage of the mandrel and in' order to accomplish this result the mandrel 11 is permitted to move forwardly in a controlled manner during the extrusion operation and in this way the force exerted on the mandrel is materially reduced. This result is provided by permitting fluid to be forced from the retraction cylinders 13 through the pipe 23 and throttle valve 56 to the drain pipe 32 and the throttle valve 56 may be adjusted to retard forward movement of the mandrel 11 to the desired degree. This setting of the throttle valve 56 is largely determined by the particular material being extruded, the length of the billet as well as the degree of deformation of the billet during the extrusion operation and also by the size of the mandrel and other factors. The throttle valve 56 may be automatically adjusted during the extruding operation by means of a switch 38 disposed in the path of movement of the platen 6 and engagement of the switch 38 by the platen 6 results in movement of the relay 42 in the switch box 37 from one position to the other to adjust the throttle valve 56 in accordance therewith and depending upon the position of the relay 42 the effect of the throttle valve 56 will either be increased 7 or decreased. If desired, a plurality of switches 38 may be provided in order that progressive adjustment of the throttle valve 56 may be aflorded and where such an arrangement is utilized, the same would normally operate to stop forward movementof the mandrel it simultaneously with completion of the extrusion Upon completion of the extrusion operation, the platen 6 engages a switch 39 which operates to close the inlet valve 58 and open the outlet 59 and switch 39 also operates to open the relay 41 which renders the switch box 37 inoperative. Consequently, the valves 50, 51, 54 and 55 connected with the switch box 37 remain in the same condition as during the extruding operation.

A pressure gauge tl'is connected to the ram cylinder 8 and the pressure gauge includes a suitable electrical contact which is connected to the valve 53 and valve 55 and when the pressure in the ram cylinder d has reached zero as the result of closing of inlet valve 58 and opening of outlet valve 59 the contact in the pressure gauge 60 operates to close the valve 55 and open the valve 53. This results in the flow of pressure fluid into the mandrel retracting cylinders 13 which results in moving the mandrel 1i rearwardly to the position shown in the drawing.

.During this rearward movement of the mandrel ll, fluid within the piercing cylinder 16 is forced outwardly through the pipe 22, valve 5'7 and check valve 51 into the low pressure tank 25. In this connection, it is to be noted that the check valve 51 is still in a condition to permit flow of fluid therethrough in either direction.

The ram 5, the platen 6 and ram piston 7 are moved rearwardly in any desired manner to the position shown in the drawing and upon reaching such position a switch 44 is engaged by the platen 6 and a switch 43 connected in series with the switch 44 is engaged by the mandrel cross-bar 12 and upon closing of both of the switches 43 and 44, through a suitable electrical circuit, the inlet valve 53 is closed, the drain valve 54 is opened, valve 57 is closed and the check valve 51 is actuated to place the same in a condition to permit flow of fluid only in a direction from the tank 25 to the piercing cylinder 16. This control circuit also operates to close the relay 41 thereby ragain rendering the switch box 37 operative. The press is now in the condition shown in the drawing and prepared for a further extruding operation.

It will be seen that by the above described invention, there has been provided a relatively simple, yet highly effective, apparatus for preventing breakage of a piercing mandrel during an extruding operation in which the extrusion operation may be carried out expeditiously without interference therewith and in which the means for preventing breakage of the mandrel is entirely automatic in operation. Conventional electric relays and switches are utilized and also conventional electrically controlled valves.

It will be obvious to those skilled in th eart that vari-.

ous changes may be made in the invention without departing from the spirit and scope thereof and therefore the invention is not limited by that which is shown in the drawing and described in the specification, but only as indicated in the appended claims.

What I claim is:

1. A hydraulic metal tube extrusion press comprising a container for a billet to be extruded, a die disposed at one end of the container, a hollow press ram movable towards said container from the side opposite said die, hydraulic means for moving said ram, a piercing mandrel extending through said ram and movable with respect thereto, piston and cylinder'means for moving said mandrel forwardly to pierce a billet disposed in said container, retracting means for moving said mandrel rearwardly and including a piston and cylinder, a conduit for supplying pressure fluid to said retracting cylinder, an inlet valve in said conduit, a drain conduit connected to said supply conduit between said inlet valve and said retracting cylinder, a drain valve in said drain conduit, a second drain conduit connected to said supply-conduit between said inlet valve and said retracting cylinder and an adjustable throttle valve in said second drain conduit,

whereby with said inlet valve closed and said drain valve open and upon forward movement of said mandrel to pierce the billet fluid will flow freely from said retracting cylinder through said supply conduit and said first drain conduit and'upon completion of the piercing operation and during the following extrusion operation with said drain valve closed, further forward movement of said mandrel forces fluid from said retracting cylinder through said supply conduit, said throttle valve and said second drain conduit, said further forward movement of said mandrel being retarded to a degree determined by the adjustment of said throttle valve, subsequent closing of said throttle valve and opening of said inlet valve serving to admit pressure fluid to said retraction cylinder to retract said mandrel.

2. An extrusion press as defined in claim 1, in which a switch is disposed at a predetermined point in the path of movement of said ram and electrical control means connecting said switch and said throttle valve, whereby upon said ram engaging said switch to operate the same the adjustment of said throttle valve will be varied.

3. An extrusion press as defined in claim 1, in which said throttle valve is manually controlled.

4. An extrusion .press as defined in claim 1, in which a low pressure fluid source is connected to the piston and cylinder means for moving said mandrel forwardly and including valve means to control the flow of low pressure fluid to move said mandrel forwardly into engagement with the billet prior to initiating the piercing operation.

References Cited by the Examiner UNITED STATES PATENTS 888,299 5/08 Benjamin 2073 1,582,696 4/26 Schlenstedt 207-3 2,006,080 6/35 Wefing 2073 2,905,317 9/59 Arenz 2073 FOREIGN PATENTS 629,311 4/ 36 Germany. 131,181 8/19 Great Britain.'

MICHAEL v. BRINDIYSI, Primary Examiner. 

1. A HYDRAULIC METAL TUBE EXTRUSION PRESS COMPRISING A CONTAINER FOR A BILLET TO BE EXTRUDED, A DIE DISPOSED AT ONE END OF THE CONTAINER, A HOLLOW PRESS RAM MOVABLE TOWARDS SAID CONTAINER FROM THE SIDE OPPOSITE SAID DIE, HYDRAULIC MEANS FOR MOVING SAID RAM, A PIERCING MANDREL EXTENDING THROUGH SAID RAM AND MOVABLE WITH RESPECT THERETO, PISTON AND CYLINDER MEANS FOR MOVING SAID MANDREL FORWARDLY TO PIERCE A BILLET DISPOSED IN SAID CONTAINER, RETRACTING MEANS FOR MOVING SAID MANDREL REARWARDLY AND INCLUDING A PISTON AND CYLINDER, A CONDUIT FOR SUPPLYING PRESSURE FLUID TO SAID RETRACTING CYLINDER, AN INLET VALVE IN SAID CONDUIT, A DRAIN CONDUIT CONNECTED TO SAID SUPPLY CONDUIT BETWEEN SAID INLET VALVE AND SAID RETRACTING CYLINDER, A DRAIN VALVE IN SAID DRAIN CONDUIT, A SECOND DRAIN CONDUIT CONNECTED TO SAID SUPPLY CONDUIT BETWEEN SAID INLET VALVE AND SAID SECOND DRAIN CONDUIT, AN ADJUSTABLE THROTTLE VALVE IN SAID SECOND DRAIN CONDUIT, WHEREBY WITH SAID INLET VALVE CLOSED AND SAID DRAIN VALVE OPEN AND UPON FORWARD MOVEMENT OF SAID MANDREL TO PIERCE THE BILLET FLUID WILL FLOW FREELY FROM SAID RETRACTING CYLINDER THROUGH SAID SUPPLY CONDUIT AND SAID FIRST DRAIN CONDUIT AND UPON COMPLETION OF THE PIERCING OPERATION AND DURING THE FOLLOWING EXTRUSION OPERATION WITH SAID DRAIN VALVE CLOSED, FURTHER TOWARD MOVEMENT OF SAID MANDREL FORCES FLUID FROM SAID RETRACTING CYLINDER THROUGH SAID SUPPLY CONDUIT, SAID THROTTLE VALVE AND SAID SECOND DRAIN CONDUIT, SAID FURTHER FORWARD MOVEMENT OF SAID MANDREL BEING RETARDED TO A DEGREE DETERMINED BY THE ADJUSTMENT OF SAID THROTTLE VALVE, SUBSEQUENT CLOSING OF SAID THROTTLE VALVE AND OPENING OF SAID INLET VALVE SERVING TO ADMIT PRESSURE FLUID TO SAID RETRACTION CYLINDER TO RETRACT SAID MANDREL. 